• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 46
  • 12
  • 3
  • 2
  • 2
  • Tagged with
  • 69
  • 69
  • 69
  • 9
  • 9
  • 8
  • 8
  • 7
  • 6
  • 6
  • 5
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

����C-CP MAS NMR study of decomposition of five coniferous woody roots from Oregon

Hawkins, Robert E. 25 July 2002 (has links)
Using ����C cross polarization magic angle spinning nuclear magnetic resonance techniques on 5 species of dead trees from the northwest (western hemlock, Douglas fir, Sitka spruce, lodgepole pine and ponderosa pine) I tracked the lignin and cellulose content over a 22 to 36 year period in order to determine the effects of decay fungi, if any, that is attacking certain species of tree. I had samples from the wood of the roots, the bark on the roots and, in some cases, the resin core of the roots. The Department of Forest Science at Oregon State University has studied this problem by using wet chemical analysis, and direct visual observation. Mark Harmon and Hua Chen of the Department of Forest Science believe that white rot occurred most frequently in the lodgepole pine and ponderosa pine and brown rot was more frequent in the Douglas-fir and Sitka spruce. Western hemlock seemed to have both brown and white rots active. The Douglas fir bark sample showed definite decomposition consistent with white rot during the first 10 years. The ponderosa pine sap showed decomposition consistent with white rot in the 10 to 22 year period. Sitka Spruce showed some decomposition consistent with white rot in the bark from 7 to 33 years, and the western hemlock showed some decomposition consistent with white rot in the sap in the first 10 years. The decompositions consistent with brown rot were much easier to see in this study. Virtually all the sap and bark samples showed decomposition consistent with brown rot at some point. The Douglas fir was the only species, other than lodgepole pine, not to show any decomposition consistent with brown rot in the bark of the tree, only decomposition consistent with white rot. The Douglas fir did show a decay consistent with brown rot in the sap for the first ten years. Ponderosa pine showed evidence of decay that brown rot would cause for the first 10 years in the sap and the bark. The Sitka spruce species analysis showed brown rot type decay in the bark for the first 7 years and in the sap for the entire time studied of 33 years. The lodgepole pine was the only species to not show any brown rot type decay in the sap or bark for the entire 22 year period studied. The western hemlock was distinct by not showing any definitive brown rot type decay for the first 10 years, but showed massive decay consistent with brown rot in both sap and bark during the following 26 years studied. I used an 8 Tesla magnet and the MAS frequency was at 5 kHz. The recycle time was 1.5 seconds and the contact time was 1 ms. I generally took about 10,000 acquisitions per sample, which added up to about 4 hours total acquisition time per sample. Presence of these rots shows that certain species are more susceptible than others, and also shows that local environmental conditions can contribute to rot susceptibility. / Graduation date: 2003
62

Forest fire drives long-term community changes of wood-decaying fungi in a boreal forest archipelago

Gudrunsson, Mikael January 2013 (has links)
Conservation of wood-decaying fungi requires improved knowledge about the long-term effects of forest management; regarding habitat loss, fragmentation and fire suppression. To better understand such effects, I examined the influence of area, isolation, fire history and forest stand characteristics on communities of wood-decaying fungi. Species richness and composition were studied along a gradient of 22 forested islands varying in size (0.16 to 17.58 ha) and fire history (spanning 5000 years) in a boreal forest archipelago in northern Sweden. A total of 490 records of 41 polypore species were found in 33 circular plots, each 0.1 ha in size. Species richness and the number of red-listed species were analyzed using generalized linear models (GLMs), while species composition was examined using non-metric multidimensional scaling (NMDS) ordination. The species composition was clearly different between recent-fire (< 300 years since last fire) and old-fire (≥ 300 years since last fire) islands, mirroring the shift in tree species composition as pine-associated fungal species were replaced by spruce-associated fungal species. The volume of logs was the only variable influencing the species richness, although the diversity of logs showed a clear trend of also influencing species richness positively. The results demonstrate the importance of having both recent-fire and old-fire forests as landscape-level habitats and species pools, where fire naturally would constitute a key role for maintaining forest biodiversity in the boreal forest landscape. The results also stress the importance of dead wood for species richness at the individual forest stands.
63

Význam rozkladu dřeva houbami v ekosystémech přirozeného lesa / Importance of fungal decomposition of wood in the ecosystems of natural forests

Štercová, Lucie January 2017 (has links)
The decomposition of organic substrates represents an important part of the global carbon cycle and affects its global change through CO2 release. In temperate forests, deadwood represents a large carbon stock, its amount and decomposition is crucial for ecosystem biodiversity and functioning. The fungi are omnipresent powerful decayers in all terrestrial ecosystems. Their ability to decompose all deadwood compounds, mainly lignocellulose, is highly important. Without fungi, the wood decompositions and the release of withheld nutrients back to nutrient cycles couldn't be performed. While many studies were concerned with the estimation of decomposition rates of deadwood, still deeper knowledge about microbial decomposition processes and the diversity of saproxylic species and their interaction is needed. The fungi are still underrepresented in dead wood studies. This study had two main objectives. First was to describe the fungal community on downed deadwood of Fagus sylvatica and Abies alba in natural forest of Salajka in the Czech Republic, to reflect the substrate changes during the different decay stages, and to link the enzyme activities to fungal community composition and their described ecophysiologies. Second aim was to describe the fungal communities on standing and downed dead logs of...
64

The ecology and population biology of two litter decomposing basidiomycetes

Murphy, John F. 30 June 2009 (has links)
Four 286m2 plots on alternate sides of the spur ridges on Brush Mt. were established and their plant communities characterized. Agaric and Bolete basidiomycetes were sampled for two years. Fifty species were recorded on the plots. Phenologically, decomposer species were highly dependent upon rainfall events, whereas mycorrhizal species were more seasonal. Two species emerged as dominant litter decomposers. Marasmiellus praeacutus (Ellis) Halling is dominant on southwest facing slopes and occurs on a wide variety of coniferous and hardwood detritus. Collybia subnuda (Ellis ex. Peck) Gilliam is dominant on northeast facing slopes, and occurs on hardwood leaves and small woody detritus. The population structure of both of these species was investigated using tests of somatic incompatibility. Genets of both species are able to persist for more than one year. The observed minimum population density is 0.071 - 0.121 genets/m² for M. praeacutus and 0.039 - 0.093 genets/m² for g. subnuda. Mating tests indicate that M. praeacutus is heterothallic and tetrapolar, and that C. subnuda is heterothallic and bipolar. Preliminary crosses between monokaryotic tester sets indicate a surprisingly low number of mating alleles in both species. Decomposition studies suggest that while the restricted distribution of ~. subnuda to the northeast slopes may be affected by substrate specificity, the restriction of M. praeacutus to the southwest slopes is due to other factors. / Master of Science
65

Ekologie hub, asociovaných s tlejícím dřevem v ekosystémech přirozených lesů / Ecology of deadwood-associated fungi in the ecosystems of nature-like forests

Zrůstová, Petra January 2014 (has links)
Dead wood plays an important role in forest ecosystems in the context of C dynamics, nutrient cycling, forest regeneration and biodiversity. Decaying wood sustains biodiversity by providing habitats and energy for fungi, bacteria, invertebrates, and many other organisms. Dead wood is resistant to decomposition and its decay is driven mainly by filamentous fungi. Community structure of wood- inhabiting fungi changes during decomposition, but the relationship between substrate quality and decomposer community is still poorly understood. This work studied fungal community composition with respect to tree species, stage of decay, volume and physico-chemical properties (such as pH, carbon and nitrogen content) of dead wood. Fungi were identified using next generation sequencing approaches - 454-pyrosequencing and Illumina MiSeq sequencing. Tree species, volume of dead wood (branches x logs) and stage of decay were the main variables affecting fungal community composition. Higher enzyme activities and content of fungal biomass indicate faster colonization of small branches than tree trunks by fungi. Fungal community composition, wood chemical properties and enzyme activities changed during decomposition. Both content of nitrogen and fungal biomass increased during decomposition. Enzyme activites peaked...
66

Caracterização de compostos de baixa massa molar redutores de ferro produzidos por fungos e mediação da reação de fenton para degradação de polissacarídeos e lignina / Characterization of low molecular weight Fe3+-reducing compounds produced by fungi and mediation of Fenton reaction to degrade polysaccharides and lignin

Valdeir Arantes 08 August 2008 (has links)
Os fungos de decomposição branca e parda produzem enzimas para degradar os componentes da madeira, os primeiros produzem enzimas hidrolíticas e oxidativas enquanto os outros produzem principalmente enzimas hidrolíticas. A degradação de polissacarídeos e lignina por fungos de decomposição parda e branca seletiva, respectivamente, não ocorre na região imediata à hifa, e, também, não pode ser explicada unicamente por ação enzimática devido a impermeabilidade das mesmas na parede celular. Neste trabalho estudou-se o sistema degradativo não enzimático envolvendo compostos de baixa massa molar (CBMM) redutores de ferro em fungos degradadores de madeira. O fungo de decomposição parda, Wolfiporia cocos e o de decomposição branca seletiva, Perenniporia medulla-panis foram cultivados em diferentes concentrações de ferro, e a atividade redutora de Fe3+ micelial e a extracelular, assim como a produção de quelantes específicos de ferro, como derivados de ácido hidroxâmico e de catecol, foram induzidas em condição de deficiência de ferro. Os géis de SDS-PAGE dos extratos fúngicos mostraram várias proteínas negativamente reguladas por ferro em P. medulla-panis e W. cocos, principalmente para proteínas entre 10 - 30 kDa. Quando os fungos foram cultivados em diferentes fontes de carbono simples com e sem suplementação de celulose microcristalina e deficiência de ferro, produziram CBMM redutores de Fe3+, os quais tiveram a produção estimulada nos meios com celulose. Análises de eletroforese capilar dos compostos quelantes de metal extraídos dos meios que proporcionaram a maior atividade redutora (Lornitina/ celulose para P. medulla-panis e glicose/celulose para W. cocos) na presença e ausência de ferro, confirmaram que, principalmente P. medulla-panis produz compostos extracelulares que são regulados por ferro. Os CBMM purificados das frações < 5 kDa apresentaram atividade redutora de Fe3+ em pH 2,0 mesmo quando ácido oxálico foi adicionado na concentração 20 vezes maior que a concentração de Fe3+. Em pH 4,5, a atividade redutora foi detectada até uma concentração de ácido oxálico 10 vezes superior a de Fe3+. Em ambos os casos a atividade redutora foi observada quando Fe3+ estava presente na forma livre ou complexada como Fe(oxalato)+. Dentre os vários CBMM produzidos por P. medulla-panis e W. cocos aqueles com atividade redutora foram o ácido 4-hidroxi-fenilacético, 1,2-dihidroxi-3-metil-benzeno, 1,2,3-trihidroxi-benzeno e o ácido 4- hidroxi-cinâmico para W. cocos, e para P. medulla-panis os principais foram 1,2-dihidroxibenzeno e 1,2,3-trihidroxi-benzeno. Além desses compostos, ambos os fungos produziram peptídeos de baixa massa molar com atividade redutora. Os CBMM redutores de Fe3+ de P. medulla-panis (Pmp) e de W. cocos (Wc) foram utilizados na ausência e presença de Fe3+ e H2O2 (reação de Fenton mediada) para oxidar polissacarídeos e lignina in vitro. Verificou-se que os maiores níveis de oxidação foram obtidos nas reações de Fenton mediadas (Wc-Fe3+/H2O2 e Pmp-Fe3+/H2O2). A degradação da celulose por estes sistemas foi caracterizada por uma rápida e extensiva despolimerização, seguida de significativa oxidação. Análises dos monômeros de lignina liberados de conífera tratada e não tratada após 13C-TMAH termoquimólise indicaram oxidação da lignina pelos sistemas Wc-Fe3+/H2O2 e Pmp- Fe3+/H2O2, principalmente por desmetoxilação e/ou desmetilação. A ação sinérgica entre os CBMM redutores de Fe3+ e as enzimas ligninolíticas ficou evidenciada para os fungos de decomposição branca Lentinula edodes, P. medulla-panis e Trametes versicolor através da oxidação do corante Azure B. / Brown and white rot fungi produce enzymes to degrade wood. The former produce hydrolytic and oxidative enzymes while the latter produce mainly hydrolytic enzymes. The degradation of polysaccharides and lignin by brown and white-rot fungi, respectively, do not occur next to the fungal hyphae and cannot be explained only by the enzymatic action due to the small pore size of sound wood. In this work, it was studied a non-enzymatic degradative system involving low molecular weight compounds (LMWC) with Fe3+-reducing activity in wood decay fungi. The brown rot fungus Wolfiporia cocos and the selective white rot Perenniporia medulla-panis were grown under varying concentration of iron. The micelial and extracellular Fe3+-reducing activity as well as the production of specific iron chelators (catechol and hydroxamate derivatives) were induced under iron starvation. SDS-PAGE gels of cellular proteins showed several proteins negatively iron-regulated in P. medulla-panis and in W. cocos, especially for proteins of 10 - 30 kDa. When the fungi were grown with different simple carbon source with and without microcrystalline cellulose supplementation and under iron restriction, they produced LMWC with Fe3+-reducing activity, which production was stimulated in the presence of cellulose. Capillary electrophoresis analyses of metal chelating compounds extracted from the growth media that promoted the highest Fe3+-reducing activity (L-ornithine/cellulose for P. medulla-panis and glucose/cellulose for W. cocos) in the presence and absence of iron, confirmed that, especially P. medulla-panis produces extracellular compounds that are iron-regulated. LMWC purified from these media showed Fe3+-reducing activity at pH 2.0 even when oxalic acid was added up to 20 fold the iron concentration. At pH 4.5, the Fe3+-reducing activity was detected at an oxalic acid concentration up to 10 fold the iron concentration. In both cases the LMWC were capable of reducing Fe3+ only when it was in its free form or complexed with oxalate to form Fe3+-monooxalate complex (Fe(C2O4)+). Among the several LMWC produced by P. medulla-panis and W. cocos those with Fe3+-reducing capability were 4-hydroxy-phenylacetic acid, 1,2- dihydroxy-methyl-benzene, 1,2,3-trihydroxy-benzene and 4-hydroxy-cinnamic acid to W. cocos and 1,2-dihydroxy-benzene, and 1,2,3-tri-hydroxy-benzene to P. medulla-panis. Both fungi also produce low molecular weight peptides with Fe3+-reducing capability. The purified LMWC with Fe3+-reducing activity from P. medulla-panis (Pmp) and from W. cocos (Wc) were utilized in the presence and absence of Fe3+ and H2O2 (mediated Fenton reaction) to oxidize polysaccharides and lignin in vitro. The highest oxidation levels were obtained with mediated Fenton reactions (Wc-Fe3+/H2O2 e Pmp-Fe3+/H2O2). Cellulose degradation by these systems was characterized by a rapid and extensive depolymerization followed by significant oxidation. Analyses of the lignin monomers released from treated and untreated softwood after 13C-TMAH thermochemolysis indicated lignin oxidation by the Wc-Fe3+/H2O2 and Pmp-Fe3+/H2O2 systems, mainly by demethoxylation and/or demethylation. The synergistic action between LMWC with Fe3+-reducing activity and the ligninolytic enzymes was evidenced to the white rot fungi Lentinula edodes, P. medulla-panis and Trametes versicolor with Azure B oxidation assays.
67

Caracterização de compostos de baixa massa molar redutores de ferro produzidos por fungos e mediação da reação de fenton para degradação de polissacarídeos e lignina / Characterization of low molecular weight Fe3+-reducing compounds produced by fungi and mediation of Fenton reaction to degrade polysaccharides and lignin

Arantes, Valdeir 08 August 2008 (has links)
Os fungos de decomposição branca e parda produzem enzimas para degradar os componentes da madeira, os primeiros produzem enzimas hidrolíticas e oxidativas enquanto os outros produzem principalmente enzimas hidrolíticas. A degradação de polissacarídeos e lignina por fungos de decomposição parda e branca seletiva, respectivamente, não ocorre na região imediata à hifa, e, também, não pode ser explicada unicamente por ação enzimática devido a impermeabilidade das mesmas na parede celular. Neste trabalho estudou-se o sistema degradativo não enzimático envolvendo compostos de baixa massa molar (CBMM) redutores de ferro em fungos degradadores de madeira. O fungo de decomposição parda, Wolfiporia cocos e o de decomposição branca seletiva, Perenniporia medulla-panis foram cultivados em diferentes concentrações de ferro, e a atividade redutora de Fe3+ micelial e a extracelular, assim como a produção de quelantes específicos de ferro, como derivados de ácido hidroxâmico e de catecol, foram induzidas em condição de deficiência de ferro. Os géis de SDS-PAGE dos extratos fúngicos mostraram várias proteínas negativamente reguladas por ferro em P. medulla-panis e W. cocos, principalmente para proteínas entre 10 - 30 kDa. Quando os fungos foram cultivados em diferentes fontes de carbono simples com e sem suplementação de celulose microcristalina e deficiência de ferro, produziram CBMM redutores de Fe3+, os quais tiveram a produção estimulada nos meios com celulose. Análises de eletroforese capilar dos compostos quelantes de metal extraídos dos meios que proporcionaram a maior atividade redutora (Lornitina/ celulose para P. medulla-panis e glicose/celulose para W. cocos) na presença e ausência de ferro, confirmaram que, principalmente P. medulla-panis produz compostos extracelulares que são regulados por ferro. Os CBMM purificados das frações < 5 kDa apresentaram atividade redutora de Fe3+ em pH 2,0 mesmo quando ácido oxálico foi adicionado na concentração 20 vezes maior que a concentração de Fe3+. Em pH 4,5, a atividade redutora foi detectada até uma concentração de ácido oxálico 10 vezes superior a de Fe3+. Em ambos os casos a atividade redutora foi observada quando Fe3+ estava presente na forma livre ou complexada como Fe(oxalato)+. Dentre os vários CBMM produzidos por P. medulla-panis e W. cocos aqueles com atividade redutora foram o ácido 4-hidroxi-fenilacético, 1,2-dihidroxi-3-metil-benzeno, 1,2,3-trihidroxi-benzeno e o ácido 4- hidroxi-cinâmico para W. cocos, e para P. medulla-panis os principais foram 1,2-dihidroxibenzeno e 1,2,3-trihidroxi-benzeno. Além desses compostos, ambos os fungos produziram peptídeos de baixa massa molar com atividade redutora. Os CBMM redutores de Fe3+ de P. medulla-panis (Pmp) e de W. cocos (Wc) foram utilizados na ausência e presença de Fe3+ e H2O2 (reação de Fenton mediada) para oxidar polissacarídeos e lignina in vitro. Verificou-se que os maiores níveis de oxidação foram obtidos nas reações de Fenton mediadas (Wc-Fe3+/H2O2 e Pmp-Fe3+/H2O2). A degradação da celulose por estes sistemas foi caracterizada por uma rápida e extensiva despolimerização, seguida de significativa oxidação. Análises dos monômeros de lignina liberados de conífera tratada e não tratada após 13C-TMAH termoquimólise indicaram oxidação da lignina pelos sistemas Wc-Fe3+/H2O2 e Pmp- Fe3+/H2O2, principalmente por desmetoxilação e/ou desmetilação. A ação sinérgica entre os CBMM redutores de Fe3+ e as enzimas ligninolíticas ficou evidenciada para os fungos de decomposição branca Lentinula edodes, P. medulla-panis e Trametes versicolor através da oxidação do corante Azure B. / Brown and white rot fungi produce enzymes to degrade wood. The former produce hydrolytic and oxidative enzymes while the latter produce mainly hydrolytic enzymes. The degradation of polysaccharides and lignin by brown and white-rot fungi, respectively, do not occur next to the fungal hyphae and cannot be explained only by the enzymatic action due to the small pore size of sound wood. In this work, it was studied a non-enzymatic degradative system involving low molecular weight compounds (LMWC) with Fe3+-reducing activity in wood decay fungi. The brown rot fungus Wolfiporia cocos and the selective white rot Perenniporia medulla-panis were grown under varying concentration of iron. The micelial and extracellular Fe3+-reducing activity as well as the production of specific iron chelators (catechol and hydroxamate derivatives) were induced under iron starvation. SDS-PAGE gels of cellular proteins showed several proteins negatively iron-regulated in P. medulla-panis and in W. cocos, especially for proteins of 10 - 30 kDa. When the fungi were grown with different simple carbon source with and without microcrystalline cellulose supplementation and under iron restriction, they produced LMWC with Fe3+-reducing activity, which production was stimulated in the presence of cellulose. Capillary electrophoresis analyses of metal chelating compounds extracted from the growth media that promoted the highest Fe3+-reducing activity (L-ornithine/cellulose for P. medulla-panis and glucose/cellulose for W. cocos) in the presence and absence of iron, confirmed that, especially P. medulla-panis produces extracellular compounds that are iron-regulated. LMWC purified from these media showed Fe3+-reducing activity at pH 2.0 even when oxalic acid was added up to 20 fold the iron concentration. At pH 4.5, the Fe3+-reducing activity was detected at an oxalic acid concentration up to 10 fold the iron concentration. In both cases the LMWC were capable of reducing Fe3+ only when it was in its free form or complexed with oxalate to form Fe3+-monooxalate complex (Fe(C2O4)+). Among the several LMWC produced by P. medulla-panis and W. cocos those with Fe3+-reducing capability were 4-hydroxy-phenylacetic acid, 1,2- dihydroxy-methyl-benzene, 1,2,3-trihydroxy-benzene and 4-hydroxy-cinnamic acid to W. cocos and 1,2-dihydroxy-benzene, and 1,2,3-tri-hydroxy-benzene to P. medulla-panis. Both fungi also produce low molecular weight peptides with Fe3+-reducing capability. The purified LMWC with Fe3+-reducing activity from P. medulla-panis (Pmp) and from W. cocos (Wc) were utilized in the presence and absence of Fe3+ and H2O2 (mediated Fenton reaction) to oxidize polysaccharides and lignin in vitro. The highest oxidation levels were obtained with mediated Fenton reactions (Wc-Fe3+/H2O2 e Pmp-Fe3+/H2O2). Cellulose degradation by these systems was characterized by a rapid and extensive depolymerization followed by significant oxidation. Analyses of the lignin monomers released from treated and untreated softwood after 13C-TMAH thermochemolysis indicated lignin oxidation by the Wc-Fe3+/H2O2 and Pmp-Fe3+/H2O2 systems, mainly by demethoxylation and/or demethylation. The synergistic action between LMWC with Fe3+-reducing activity and the ligninolytic enzymes was evidenced to the white rot fungi Lentinula edodes, P. medulla-panis and Trametes versicolor with Azure B oxidation assays.
68

The role of wood decay fungi in the dynamics of a mountain spruce forest / The role of wood decay fungi in the dynamics of a mountain spruce forest

POUSKA, Václav January 2012 (has links)
This thesis is focused on environmental preferences of wood-decaying fungi and their relationships with forest structure and development. Relationships of fungi to properties of wood and forest stands were studied on the basis of field observations in Central-European mountain spruce forests. Plot-based approach was used to reveal a general pattern in the diversity of fungi within a single forest stand and between different stands. The analysis of stand structure provided a background for plot-based approach. Substrate-based approach was used to study single species preferences and their communities. In addition, the influence of wood properties (including fungi and their rots) on the regeneration of spruce on logs was studied.
69

Návrh rekonstrukce dřevěných konstrukcí stávajícího objektu / The reconstruction design of timber structures of the existing building

Bartlová, Jana January 2015 (has links)
The content of this work was to carry out construction-technical survey of timber structures of the existing building in order to design an appropriate procedure for their reconstruction. The survey showed construction in an unsatisfactory to disrepair, so further work also includes the static calculation of new structures proposed instead of the current. Timber structure in the building has form of staircase, roof and ceiling construction. Newly designed the following types of stairs and roof trusses from which the lower belts are used as ceiling beams. The new proposal also includes possible roofing, roofing options, developed one of them. The work also includes drawings, bill of materials and cost estimate staircase structure and truss. Specialization in the field of civil engineering is represented by drawings of the new truss and passport (view of current state) whole object on parcel ST.74 / 1, land Tišnov (okr.Brno-venkov), the content of which was the basis for this work.

Page generated in 0.0907 seconds